Even though shin splints occur frequently in athletes who run, nobody is entirely sure of their origin. Some researchers believe they occur when the lining on the outer surface of the tibia (the shin bone) gets inflamed. Others believe they come from microscopic fractures in the tibia. Either way, shin splints can last for months at a time, making it difficult to stay active.

How to prevent it: Because researchers are divided on what’s actually causing the pain, they are equally divided on how to prevent it. Studies have shown that popular prevention methods such as stretching the Achilles tendon, making gradual progressions in training, and wearing shock-absorbing insoles don’t show statistically significant results. And as for the commonly quoted solution of running barefoot on grass, Smith says that might lead to more injuries.

Dr. Smith also recommends strengthening and stretching the calf muscles, and increasing training volumeby no more than 10 to 20 percent per week.